The present invention relates generally to fluid handling apparatus and, more particularly, to direct response valves of reciprocating type.
It is not uncommon for subterranean reservoir rocks to be fully saturated with oil and gas yet be of such low permeability that they are not feasible to develop in an economic manner. In such cases, production rates are often boosted by resorting to hydraulic fracturing, a technique that increases rock permeability by opening channels through which reservoir fluids can flow to recovery wells. During hydraulic fracturing, a fluid such as water is pumped into the earth under extremely high pressure where it enters a reservoir rock and fractures it. Sand grains, aluminum pellets, glass beads, or other proppants are carried in suspension by the fluid into the fractures. When the pressure is released at the surface, the fractures partially close on the proppants, leaving channels for oil and gas to flow to recovery wells.
Specialized pumps are used to develop the pressures necessary to complete a hydraulic fracturing procedure or xe2x80x9cfrac job.xe2x80x9d These pumps are usually provided with so-called fluid ends within which reciprocating plungers place fluids under pressure. Suction and discharge valves control fluid flow to and from the plungers. Improperly locating a valve in the fluid end at the time of manufacture can greatly weaken the fluid end, leading to catastrophic pump failures. Similarly, a valve that has too many projections can capture or xe2x80x9cknock outxe2x80x9d enough proppant to block the flow of fluid through a pump requiring, at a minimum, that time and effort be invested to clear the blockagexe2x80x94costly undertaking in an oilfield environment.
In light of the problems associated with fluid ends of pumps used for hydraulic fracturing, it is a principal object of the invention to provide a suction valve that reduces the likelihood of proppant being knocked out of suspension to create a blockage. The suction valve of the present invention, thus, offers few impediments to flow through a fluid end when open so that fracturing fluids can flow smoothly through it. As a result, fracturing fluids with higher than normal concentrations of suspended proppants can be pumped with substantial cost savings to the user. Unlike a conventional, wing-guided valve, no spring retainer projects into the plunger bore to close the open valve and, sometimes, undesirably knock out proppants.
It is another object of the invention to provide a suction valve of the type described that may be seated in a relatively shallow pocket in a fluid end. A valve pocket of shallow depth, of course, requires less load-bearing material to be removed from the body of a fluid end than does one of greater depth like that required for a wing-guided valve. It is less likely, then, that a fluid end configured to receive the suction valve of the present invention will fail from the development of excessive internal loads and stresses.
It is a further object of the invention to provide a suction valve of the type described that utilizes a valve seat that abuts its supporting surface, i.e., a seat deck, at a shallow incline rather than at right angles as has been commonly done. This slope of about 30xc2x0 has been found to significantly reduce zones of stress transmitted through a fluid end. It is along such zones that fluid ends have been known to crack and fail under load.
It is an object of the invention to provide improved elements and arrangements thereof in a suction valve for the purposes described which is relatively lightweight in construction, inexpensive to manufacture, and dependable in use.
Briefly, the suction valve in accordance with this invention achieves the intended objects by featuring a valve seat and a piston movably joined to the valve seat. The piston has a head for engaging the top surface of the valve seat and a stem extending downwardly from the head through the valve seat. A streamlined valve guide is positioned adjacent the bottom surface of the valve seat and slidably receives the stem. A valve keeper is fitted upon the stem such that the valve guide is disposed between the valve seat and the valve keeper. A keeper pin is slidably positioned within a transverse aperture in the stem and abuts the bottom of the valve keeper. A compressed spring is positioned between, and exerts opposing forces upon, the valve guide and the valve keeper so as to normally retain the head of the piston in engagement with the top surface of the valve seat. Means are provided for preventing the unintentional separation of the keeper pin from the stem and keeper.
The foregoing and other objects, features and advantages of the present invention will become readily apparent upon further review of the following detailed description of the preferred embodiment as illustrated in the accompanying drawings.